function Pm=getPm(interface,node_number)
if((node_number<=6&&interface==2)||(interface==3&&node_number<20)||interface==4)
            Pm=2;
        elseif((node_number>6&&node_number<36&&interface==2)||(interface==3&&node_number>=20))
            Pm=3;
        elseif(interface==2&&node_number>=36)
            Pm=4;
end